FourEyes

Hello Again,

I'm having a problem tracking down the source of an intermittent (although becoming much more consistent) rough idle that I have been experiencing for the last few months. By rough I mean that the engine and therefore the truck shake a lot. Feels kind of like a misfire. I did many tests as per FSM and searched around the forum but wasn't able to find any solutions. I believe the problem to be electrical (read below).

The main symptoms are as follows:

-Varying rough idle anywhere under 1100 RPM. Worse (rougher) the lower the RPMs.

- Headlight use lowers the RPMs slightly (which I believe to be normal) therefore making it worse. Sometimes at idle/coasting the headlights will flicker or just shut off (just the headlights not interior lights) until the throttle is applied bringing the RPMs back up. Although sometimes they will not come back on even with the revs up. When the truck is shut off sometimes the headlights will turn off (just the headlights not the interior lights). If you add any significant extra load they will always shut off. The headlights will almost never turn on without the engine running and won't come on for some time until revs come up after starting. If they are able to be on while the truck is switched off they will go out upon start up and then eventually come back on.

- The truck also seems to struggle more when starting.

- The symptoms definitely worsen with added electrical load.


A few months ago I did do some rewiring in the engine bay. I moved all my electrical accessories to the side terminals of the battery. I also did the “big three upgrade” which, if you are not familiar with it, is replacing/ adding larger gauge wires to the charging system and for your main ground wires in hopes the lower resistance will help reduce voltage drop, which I was experiencing slightly (google “big three upgrade” for more clarification if needed). When I added the larger wire that is supposed to go from the alternator straight to the battery I left the stock wire in place as per many a recommendation. What always puzzled me though was that the large wire would be bypassing the voltage regulator while the stock one would continue to flow through it. I never experienced high voltage that I noticed. The only odd symptom was that the charge light would sometimes flicker at idle or lower RPMs and I could hear the relay clicking on and off. Regardless, I have removed the large gauge wire from the battery and alternator for now in hopes of reducing the number of variables while sorting this out. I have not seen any change in the rough idle (about 70% of the time as of writing this) but the headlight problem has become more frequent. I also tried disconnecting all my accessories from the battery which did not result in a change either.



Items that I have checked and their corresponding readings:

- Plugs all appear to be getting spark at idle (checked with an inline bulb style spark tester).

- Ignition system all checks out as per FSM.

- Plugs are new, gap set to FSM/ Wires are relatively new and appear to be in good shape.

- The distributor is a few years old (LCE Pro).

- New distributor cap and rotor.

- Timing is 5 degrees BTDC with vacuum advance lines plugged / advances to the first unumbered mark when vacuum is connected (as per FSM).

- Volt meter in truck (SR5) reads fine and I have checked it with another I have.

- At idle, reading around 14.5 V at the battery (with multimeter).

- Battery is an Optima red top that is only a few years old. Resting voltage is 12.5 (I feel like this should be a little higher?).

- Tested with another Optima red top of the same make/model/specs that is newer and has spent most of it's life on a trickle charger (resting voltage is 12.75). Symptoms are perhaps a little better but still very present.

- Alternator is only a few years old and seems to be charging fine (no charge light but I haven't tested it other than V at battery).

- Fusible links are relatively new and test good.

- All fuses look good.

- Carb is has been rebuilt / tested about a year or so ago by a reputable carb shop and all settings are the same as they were before when the truck was running fine. Fuel level does seem to be slightly higher in the sight glass than before but not much (I"ll double check that later though).

- Valves were adjusted to spec not too long ago.

- No vacuum leaks that I can find (new lines and tested many many times over the past few years)

- This has been happening since August in varying temps, altitudes, and climates.



In case it's helpful here is a list of parts from another unrelated thread of mine from about a year ago:

Parts of note:
- Rebuilt 22r from Yota 1 Performance in Modesto CA with approximately 12000 miles on it
- Light port/polish done to intake and head
- Stock cam
- Rebuilt Aisin carb from Recarbco in Martinez CA
- Stock air intake (with K&N filter)
- LCE street header with air injection and O2 sensor
- Custom 2” stainless exhaust (no leaks of consequence)
- New Magnaflow catalytic converter and muffler
- New cooling system that seems to be functioning perfectly
- New Toyota EGR valve / new Toyota BVSV (EGR modulator is not new)
- New LCE pro distributor / cap
- New coil and ignitor
- New plugs / newish wires
- New smog pump and functional EACV
- New fuel pump and lines
- Fresh oil and filter



Like I said above, I do believe this problem to be electrical in nature but I am open to all suggestions and questions. I have been less than stoked with the auto parts store alternator I had to put in when my alternator went out on a trip a few years back and been having been planning on getting a higher amperage one when funds allow. That said, the truck was fine up until recently so I would like to figure this out before I change yet another variable.

Please holler if you have any ideas!



Thanks,

Sam

83

Well you're being thorough, which is good. I'm not sure I can be much help, except to get a little clarification. Did the issues start after doing the wiring upgrades or were they there before?

FourEyes

Thanks for your reply!

I have tried to be thorough but seem to still be missing something, as is frequently the case, HaHa. Good question! I should have clarified that. The issues did start after the the wiring upgrades but... they started about a month later while on a 3 week long road/wheelin trip, so the truck was getting a lot of heavy use. That said, they started out as only a very occasional oddity and the headlights rarely shut off (although they did from time to time).

I have thought that it is possible that the big three upgrade bypassing the voltage meter could have damaged something, but what? I've checked all the main electrical components that I can think of that would effect idle and the headlight issue is just kinda bonkers.

Thanks again,

Sam

83

Yeah, without better electrical knowledge the best I'd be able to do is triple check all the connections in case any of them worked their way loose. The most common frustrating electrical issues are almost always grounding issues...

Is your truck one with an external voltage regulator, or is it part of the alternator? Not sure if the alternator you bought has one in it or not, since it's aftermarket. Not sure what the effect of two voltage regulators would be...

FourEyes

Yeah, I'm going to go through it all again when I get a chance but I checked most if not all the connections and they seem fine. Yeah they do tend to be grounding issues. I have multiple additional grounds added all over as well.

My truck is one with an external voltage regulator. The alternator I replaced it with should not have one as it is a direct replacement. That is interesting to think about though. My guess would be that the second one would just be redundant because the voltage would already be regulated coming out of the alternator and it would read it as normal voltage

OldBlueMidnight

When was the cooling system upgrade in relation to the symptoms? I'd look for a leaky hose connection above the alternator, and make sure the alternator itself checks out. Also, my experience with the high amp alternator was not a good one. The one I got from LC had a undersize pulley on it; not sure if that is how they all work, but the one I got would throw belts reliably. I put the correct size pulley on there to fix the problem, so now I have no clue what amperage it's putting out, and it probably isn't charging at all at idle. Wish I'd just gone for the stock replacement.

FourEyes

Thanks for your reply!

The cooling system was originally upgraded when I did the engine swap a year and a half ago or so. I have since been over it a few times working out the kinks. It is not currently leaking at all. It never leaked from either side of the elbow hose above the alternator just most other places at one time or another haha. Good thought though! Yeah I do need to do the actual FSM alternator test but to do it the way it tells you to I need to borrow another multimeter. I have had it tested via multiple auto parts stores and they all say it checks out. I don't know if I trust them though haha. Thanks for your input in the high amp alternator! I didn't even realize LCE had one. I was planning on going with one from Northwest Off-Road (https://www.northwestoffroad.com/parts/alternators.php) as I have heard a few good things about theirs. If I go that route I'll check about the pulley/belt size and what not. I did think about going with a stock Nippondenso replacement but I would eventually like to run a winch and doubt that it would be up to the task.

Thanks again, and please let me know if you have anymore thoughts!

Sam

Old83@pincher

If I'm right you have two problems, the headlights and the rough idle. I'd check the voltage at the battery, alternator and the ignition module just to rule out the charging system; I doubt its that. With a fully charged battery you should be able to get one start and be able to run for at least an hour or two without the alternator running and no additional loads I doubt that "big three" as its called now had anything to do with it, you simply added some wiring in parallel to what was already there...unless you accidently shorted something to ground!

The headlights to me sounds like a bad headlight relay/relay socket wiring. Check the voltages at the socket and if you can get a spare relay try that. Check the headlight sockets themselves...had lose sockets on my Taco that drove me nuts! Check for voltage right at the headlights. Could be the combination switch too.

The rough idle...have you checked the fuel cut-off solenoid and the wiring on the carb? If could be cutting off the fuel to the idle circuit and when you speed the engine up its no longer running on the idle circuit. Could also be the ignition module and/or ignition coil, but you said they're new. I put a new coil in mine and it idles way better. Also just prior to the module in mine quitting it did run kind of rough, but that period was only about 5 -10 minutes, then it stopped completely.

Could be that EGR modulator. Try disconnecting the vacuum hose from the modulator to the valve and see if that helps.

And just because its a new/rebuilt part don't assume and rule it out...check all the connections and grounds carefully. I had a charging problem not long ago caused by a corroded wiring crimp inside the connector!

FourEyes

Thanks for your reply!


It does seem like two problems. The reason that I suspect that they are related is that they both arrived at the same time and also worsened (became more pronounced/frequent) overtime at a pretty similar rate. Also the load applied by the headlights/accessories seems to exacerbate the idle issue even when the RPMs are in an acceptable idle range. That said, coincidences do happen and I have been planning to go over all the wiring yet again soon.

The voltage at the battery has been tested and is a pretty solid 14.28V (14.51V for the second battery, see first post) at idle with no accessories/lights on (just realized I forgot to put those numbers on the first post).

With just the headlights on it's 14.18V
With just the brights on it's 14.08V
With just my aux lights (ones I added a long time ago that were previously not a problem) it's 14.07V
With the headlights + the aux it's 13.93V
With the brights + aux lights on (the most draw I'll get from lights) it's 13.04V
(these are all with the first battery, see first post)

The idle get's rougher the higher the load/lower the V and lower the idle speed.

The headlight sockets seem to be tight and fine. I didn't think to check the V at the headlight connection. Good idea! I'll do that soon.

The fuel cut solenoid and it's corresponding vacuum switch check out as per FSM. I am also getting decent V from the harness side of the connector when I'm supposed to.

The entire ignition system is indeed relatively new and has also passed all tests as per the FSM.

I did think about that EGR modulator but hadn't tested it again. It's tricky to test right and I may have just been a bit traumatized by going over all the smog stuff last year HaHa. (see my thread from last year if you really want to know). That is a good idea though as the EGR system can definitely wreak havoc when it's messed up. I'll check it.

Yeah, I am planning on going over it all yet again soon. Maybe something will pop out at me that I somehow missed all the other millions of times I've been through it as that does truly happen. Ooph that sounds like a serious electrical gremlin headache! Glad you got it figured out!

Thanks again,

Sam